​                           ​​利用Spring IOC机制编写HttpServletUtil工具​​​


​工具目的：​

​使用servlet的缺点：​

  1. ​一个servlet类只能写一个请求方法（当然可以通过判断参数实现不同的请求），代码冗余​
  2. ​只能在doGet、doPost或者service方法中编写​

​SpringMVC的不足之处：​

  • ​编写的SpringMVC可以使用Model，ModelAndView，ModelMap等对象进行传参，​
  • ​但是！！！使用ModelAndView方法的放回类型必须的ModelAndView，使用Model和ModelMap必须写在方法的参数中​
  • ​使用原生的servlet API request和session传参必须在方法的参数中声明才能使用。​

​因此，使用​​HttpServletUtil​​配合SpringMVC可以在SpringMVC类中通过注解注入工具类直接使用request对象、response对象、application对象和session对象，并且不用把这四个对象放在方法中声明便可以传参。​


​1、在springMVC的配置文件中添加具有HTTP协议的bean和开启springmvc的注解功能​

<!-- 1. 扫描具有HTTP协议的注解bean -->
    <context:component-scan base-package="com.gxwz.web" />

    <!-- 2. 开启springmvc的注解功能 -->
    <mvc:annotation-driven />

​2、编写工具类 HttpServletUtil.java​

package com.gxwz.util;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class HttpServletUtil {

  @Autowired
  private HttpServletRequest request;
  @Autowired
  private HttpServletResponse response;
  @Autowired
  private HttpSession session;
  @Autowired
  private ServletContext application;
  
  public HttpServletRequest getRequest() {
    return request;
  }
  public HttpServletResponse getResponse() {
    return response;
  }
  public HttpSession getSession() {
    //return request.getSession();
    return session;
  }
  public ServletContext getApplication() {
    return application;
  }

}

​3、编写测试类 web.java​

package com.gxwz.web;

import java.util.ArrayList;
import java.util.List;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

import com.gxwz.util.HttpServletUtil;

@Controller
public class Web{
  
  @Autowired
  private HttpServletUtil httpServletUtil;
  
  @RequestMapping("/web")
  public String service() {
    
    List<String> list = new ArrayList<String>();
    list.add("公司大法官");
    list.add("国史大纲");
    list.add("根深蒂固");
    
    HttpServletRequest request = httpServletUtil.getRequest();
    HttpServletResponse response = httpServletUtil.getResponse();
    HttpSession session = httpServletUtil.getSession();
    ServletContext application = httpServletUtil.getApplication();
    
    System.out.println("request："+request);
    System.out.println("response："+response);
    System.out.println("application："+application);
    System.out.println("sessionId："+session.getId());
    
    request.setAttribute("list", list);
    session.setAttribute("list", list);
    application.setAttribute("list", list);
    
    return "web.jsp";
  }
}

​4、编写跳转页面 web.jsp 测试效果​

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
    <!--  -->
    <h2>欢迎访问SpringMVC测试网页</h2>
    <hr>
    <b>使用EL表达式获取：</b> ${list }
    <hr>
    <b>使用pageContext获取：</b> ${pageContextScope.list }
    <hr>
    <b>使用application获取：</b> ${applicationScope.list }
    <hr>    
    <b>使用request获取：</b> ${requestScope.list }
    <hr>
    <b>使用session获取：</b> ${sessionScope.list }
    <hr>
    
</body>
</html>

​5、运行效果​

​分享一个SpringMVC的工具类_java​


​总结：​

​​这样就可以使用工具直接使用servlet的三大作用域的对象了，是不是很方便！！！​​